1. Field of the Invention
This invention pertains to radar and communication antenna systems. More particularly this invention pertains to monopulse antenna systems wherein the antenna system provides means not only for concentrating the electromagnetic radiation pattern of the antenna but also for tracking of objects or sources within the radiation pattern of the antenna.
2. Description of the Prior Art
Numerous antenna systems have been constructed which provide means for transmitting and receiving electromagnetic energy as well as for tracking a source of such energy within the electromagnetic far-field of the antenna. Some such systems utilize a mechanically nutating feed system which moves in a periodic manner so as to cause the radiation pattern of the antenna to nutate and thus provides a means for sensing the location of a source of electromagnetic energy within the radiation pattern of the antenna. The source of such electromagnetic energy may be either an object having an active transmitter located therein or an object that reflects electromagnetic energy incident thereon.
Monopulse antennas have been constructed which utilize a fixed-feed system consisting in some instances of two or more horns arranged such that by comparison of the amplitudes and/or relative phases of the signals received at each of the horns, one can obtain sufficient information for tracking and locating an object in the far-field of the antenna.